The thrash icons’ troubled era was documented in the movie Some Kind of Monster, which covered the departure of bassist Jason Newsted, frontman James Hetfield’s alcohol issues and the breakdown of the relationship between Hetfield and Ulrich. In 2005 they opened two Stones shows in San Fransisco, as part of the British icons’ A Bigger Band world tour.

“[W]e disappeared then for about a year,” Ulrich told the Sun in a new interview. “And then the Rolling Stones called us up and said, ‘Come and play some shows with us in ­California,’ and we sort of agreed, you’re not going to say no to the Stones, so that was it. It gave us the way to start it back up again. Whether you’re a team in an office or a bunch of dudes in a rock and roll band, at some point people have to figure out how to get along and work as a team.”

He continued: “If you don’t care, it’s easier to walk away, but fortunately we cared enough about Metallica on behalf of ourselves and the fans to figure out a way to make it function. I’m happy that we did.”

Speaking at the time when the Stones appearances were announced, Ulrich had noted: “These shows will enable us to recharge our batteries, both creatively and physically, as we prepare for the next phase of Metallica.” In the new interview he reflected on how each band member had discovered their own “breaking points” and ways of “keeping clear of those edges,” saying: “We put out our first record when I was 19 and we were touring all over Europe and America. I was suddenly on a tour and helping myself to what was on offer. That’s fine, and I would dare anybody to not do that. We had a lot of fun, but you ­settle down in a relationship and have kids, and nowadays it’s treadmills, protein shakes and vegan food … You’ve got to have an awareness of what you need to do to man up, suit up and make it happen on stage.”

Despite the importance of the two shows, Ulrich recalled in 2007 that the experience hadn’t been everything Metallica could have hoped for, and that it was summed up by the moment they were asked if they’d like to be photographed alongside the Stones. “[T]his assistant… escorts us into this place in the tunnel leading into the stadium and she says, 'Wait here,’” he said. “This band Everclear – who were playing also – they were kind of like over there on their 'X'. So we're standing there and we go over and say 'Hello' to the guys in Everclear… And this assistant comes back and says, 'No. The guys in Metallica stay here, and the guys in Everclear stay over here.' We were like, 'Whoaaah.'

“So then about five minutes later the Stones come in, and I swear they didn't stop – they slowed down their pace, or their walk, just slow enough to get, like, two or three pictures taken, two or three frames shot with Everclear, and then they came over to where we were standing… Charlie Watts said 'Hello' and I think Keith [Richards] nodded or something, and Mick [Jagger] looked like we were all gonna give him pneumonia or something – he had this disgusting look on his face. And then they slowed down long enough while the photographer took two or three frames, and then they walked off. And then the assistant came over and said, 'If the band approves the photo, we'll send you a copy.’”